Methods for drill stem testing



L. l. JENSEN METHODS FOR DRILL STEM TESTING Filed July 28, 1967 as 07 72 9a 7/ Z /0 ya f a//zre/r INVENTOR. 75

7! I 14 BY dwzm g if ATTO/P/VEJ United States Patent 3,427,653 METHODS FOR DRILL STEM TESTING Lloyd 1. Jensen, Calgary, Alberta, Canada, assignor, by

mesne assignments, to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Original application, June 21, 1965, Ser. No. 465,432, now Patent No. 3,353,609. Divided and this application July 28, 1967, Ser. No. 671,515

Claims priority, application Canada, May 4, 1965,

U.S. Cl. 166-264 6 Claims Int. Cl. E21b 49/00, 23/ 06 ABSTRACT OF THE DISCLOSURE Methods for drill stem testing include the steps of lowering a packer, a tester, and a closed chamber into a well bore on a pipe string, setting the packer and opening the tester to permit formation fluids to flow into the chamber, closing the tester to trap the sample in the chamber and then unseat-ing the packer, raising the closed chamber toward the surface and when its upper end reaches the surface, connecting the upper end of the chamber to a receptacle, opening the lower end of the chamber to the well annulus, and then applying fluid pressure to the well annulus to circulate the sample out of the chamber and into the receptacle.

This is a division of application Ser. No. 465,432, filed June 21, 19 65, new U.S. Patent No. 3,353,609.

This invention rel-ates to formation test-ing and, more particularly, to methods for obtaining recovery of fluid samples from a well bore.

During the drilling of a well, the operator may at some time desire to test a section of the well for production potential. To do this, a testing tool having a normally closed tester valve and a packer means is inserted into the well at the lower end of a string of pipe or tubing. The packer means is disposed at a location just above the section to be tested and expanded to close off the bore of the well. Thus, the section for test is isolated from the drilling control fluid which is usually mud. The testing tool includes a pressure recorder which measures the initial pressure of the isolated section to obtain What is referred to as an initial shut-in pressure. The tester valve is then opened and format-ion fluids flow into the string of tubing. The flow may appear at the surf-ace if the pressures are great enough. Pressure is recorded during the flow period. The tester valve is then closed and a final shut-in pressure recorded.

When the string of tubing is brought to the surface and sections of tubing and tools are removed from the string of tubing, the formation fluids in the tubing are exposed at the surface or floor of the drilling platform. Such exposure of formation fluids may be undesirable under certain cricumstances for reasons of safety or secrecy.

Sometimes, during the testing operation, the tools become stuck in the well bore. A safety joint is normally provided in such tool strings to permit removal of the pipe above the stuck portion. However, it is often necessary to lower a free point indicator and then an explosive string shot through the bore of the pipe to loosen the threads in a drill collar, in event that the pipe is stuck above the safety joint, and thereby uncouple the string of tools at that point. In the event that the use of a free point indicator and string shot is warranted, the pipe and tools mus-t have a bore therethrough to receive these devices which are lowered into the pipe by means of a cable.

Further, due to the extended periods of time sometimes required to operate a safety joint or loosen a drill collar,

3,427,653 Patented Feb. 11, 1969 the drilling mud in the well bore must be circulated to prevent the drilling mud from setting up. Such circulation also will prevent any gas which may be entering the 'well bore from aerating the column of mud. By continuously circulating the mud to the surface, the gas is permitted to escape from the mud and thereby maintain the mud density at a safe value. The circulation of mud in the well bore will also prevent further sticking of the pipe or tubing above the initial stuck point. Additionally, oil is sometimes spotted about the stuck point to free the pipe from the wall of the well bore.

It has often been undesirable heretofore to test wells at night since it is necessary to keep electrical equipment running in order to provide light. The presence of such electrical power at the well head may present a hazard if flammable formation fluids and gases are exposed at the surface during testing operations.

The present invention is directed to methods to be performed during the testing operation to prevent uncontrolled flow of formation fluids at the surface. The formation fluids are contained in the tool string to prevent uncontrolled escape at the earths surface and may be transferred to closed containers or covered pits so that the results of the test are confidential. The apparatus is constructed to provide for the lowering of a free point indicator, string shot, or other device into the tools and to permit circulation of drilling mud in the well bore in the event the tools become stuck in the well bore.

Accordingly, it is an object of the present invention to provide new and improved methods for conducting drill stem tests.

Another object of the present invention is to provide a new and improved method for conducting drill stem tests wherein the results of the test are confined within a closed chamber and removed therefrom into convenient receptacles at the earths surface.

Still another object of the present invention is to provide a new and improved method for conducting a closed chamber drill stem test which permits the use of a free point indicator and string shot to loosen joints in the apparatus and also permits circulation of drilling mud in the well bore while the drill stern test appaartus is in the Well bore.

Therefore, in accordance with the present invention, in a drill stern test, the fluid recovery is limited to a given portion of the drill pipe forming a closed chamber and is transferred into a closed system at the earths surface. The fluid recovery enters the closed chamber through a test valve in the string of tools. Means are provided at the upper end of the chamber to contain the fluids therein. After suflicient fluid sample has been taken, the test valve is closed. Selectively operable means are provided for reversing the fiuids out of the chamber into a convenient receptacle either before or after the string of tools is retrived to the surface. The means for closing off the chamber is provided with a plug which may be selectively removed when the tool is in the well bore to provide an open bore through the string of tools 'for reception of apparatus lowered on a cable.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a string of tools in a well bore for practicing the present invention;

FIG. 2 illustrates a view in cross section of apparatus embodying the present invention; and

FIG. 3 is a view taken along line 33 of FIG. 2.

FIGURE 1 illustrates a drill or tubing string 11 which is lowered from the surface of the earth into a well bore 12. At the lower end of the drill string 11 is a conventional testing tool string 13 such as the type illustrated and described in US. Patent No. 2,901,001. The usual drill stem testing tool string 13 includes a tester tool 13a having a flow tube with a normally closed valve (not shown) and a packer element 14. The packer element 14, when actuated as shown, expands into sealing engagement with the borehole wall. After the tester valve is opened, fluid flows from below the packer 14 through its flow tube and into the tubing string. Pressure recorders (not shown) in the tool string 13 measure and record pressures. A bypass valve 15 is positioned in the tool string below the tester to permit well fluid to bypass the packer when the tool string is being lowered into the well bore. A safety joint 16 is positioned in the tool string above the packer to permit removal of the string of pipe above the packer should the packer or perforated anchor 17 become stuck in the well bore. As shown in FIG. 1, the perforated anchor 17 is positioned on the lower end of the string of tools for admitting well fluid to the flow tube and for engaging the bottom of the well bore to expand the packer in a conventional manner.

It will be appreciated that hook-Wall packers (not shown), which can be set without a bottom hole anchor, could be employed rather than the type described.

A reversing sub 18 couples the lower end of a section of drill pipe 19 to the tester tool string 13. An isolation sub 20 is coupled to the upper end of pipe section 19. The portion of pipe 19 will normally be comprised of several sections of pipe to form a closed chamber of any desired length for receiving a formation fluid sample. It has been found that about 1000 feet of pipe provides a sufficient chamber for testing most wells.

The reverse circulation valve sub 18 is provided with hollow knock-out plugs which seal off ports 27 in the outer wall of the sub. Plugs 25 are constructed so that a weighted member dropped thereon will break the plugs and open an interior bore 29 of the sub to fluid communication with the Well bore through ports 27.

The isolation sub 20 releasably supports a bar 33 by means of a retainer pin 35 which pin is operable from the exterior of the sub 20 to release the bar 33. Release of the bar 33 permits the bar to drop to the lower end of the chamber 19 and into bore 29 in sub 18 to break the plugs 25 thus opening ports 27. A bar stop (not shown) is provided below the knock-out plugs 25 to stop the falling bar 33.

FIGURE 2 is a detailed view of the isolation sub 20. This sub includes a housing 21 having threaded box and pin ends 37 and 39 for connection in a string of tubing. A bore 41 extending longitudinally through the sub forms a flow passage. An inwardly extending shoulder 42 is \formed in the bore 41 at the upper end thereof to form a restriction in the bore. An intermediate shoulder portion 43 forms a lesser restriction in the bore below shoulder 42.

A cylinderical knock-out plug 44 is positioned within the intermediate portion 43 of bore 41 with the upper surface 45 of the plug abutting the shoulder 42. The plug 44 is sized for close fitting but sliding reception within the intermediate shoulder portion 43. An annular recess 46 is formed in the outer peripheral surface of the plug midway between its top and bottom. O-ring seals 48 are positioned in annular grooves above and below the recess 46. The lower end of the plug has a threaded recessed portion 50 for receiving the upper threaded end of the weighted drop bar or dart 33. A transverse bore 54 is formed through the wall of sub housing 21. An enlarged portion is formed in the outer end of bore 54 and is threaded. The drop bar retainer pin 35 is positioned in the bore 54 with one end of the pin extending into the recess 46 in plug 44. A threaded end portion 58 on the pin is received in the threaded portion of bore 54. The end portion 58 is provided with a recess 60 to accommodate a wrench or tool to rotate the threaded pin for withdrawal from the recess 46 in plug 44.

A valve assembly 63 in sub 20 is best shown by referring to FIG. 3. The valve 63, shown in a closed position, has a body portion 65 threadedly received in a valve bore 67 and has a tapered end portion 69 provided with an O-ring 70. When the valve body 65 is rotated in one direction, the tapered end portion 69 seats in a valve seat 71 to block or close off a transverse fluid passageway 72 which extends through the wall of housing 21. The passageway 72 provides for fluid communication between exterior port 86 of the sub 20 and the flow passage 41. R0- tation of the valve body 65 is accomplished by means of a wrench or the like applied to a wrench access 74 in the body 65 through a bore 73 opening to the exterior of the housing. Thus, the valve has a control portion exposed to the exterior of the sub. An enlarged body portion 64 of the valve 63 is provided with an O-ring to form a fluid tight seal with the bore 73. A snap ring 75 is received in a snap ring groove to maintain the valve body in the bore 73.

A passageway 76 connects with the seat end 71 of the valve bore 67. An enlarged threaded portion 78 is provided at the end of the passageway to receive a threaded access plug 80. An O-ring seal 82 is provided on the plug to seal the end of the passageway. A wrench access 84 is formed on one end of the plug to facilitate its removal from the threaded end portion of the passageway 76. The wrench is inserted into the access through the port or bore 86 opening to the exterior of the sub housing 21. When the access plug is removed, the threaded portion 78 provides a means for connecting a flow line to the valved sub.

The passageway 72, which opens to the flow passage 41, is formed in the housing by boring from the outside of the housing 21. A threaded end portion 88 of the passageway 72 opening to the exterior of the sub housing receives a threaded plug 90 with seal means to close off the passageway to the exterior of the sub. Wrench access means 92 are formed in the plug to provide for insertion and removal of the plug.

In operation, the test tool string 13 is lowered into the well bore at the end of a string of tubing or pipe 11, the test valve 13a of the tool string being closed. Above the tool string 13 is pipe section 19 with isolation sub 20 secured to its upper end. Valve 63 in isolation sub 20 is positioned so close off passageway 72 and thereby isolate the upper end of chamber 19.

At the level in the well bore where the test is desired, the packer is actuated into sealing engagement with the well bore and the test valve 13a of tool string 13 is opened permitting formation fluids from formations isolated below the packer to flow into the perforated anchor and thence into the pipe section or chamber 19. It is readily seen that any amount of pipe may be included within this section defining chamber 19, the amount depending upon the duration of the formation test. It may be desirable to take several shut-in tests on the formation with intermediate flow periods. At the end of the flow period, the test valve of the tool string 13 is closed, thus closing off the lower end of the pipe section 19 leaving a sample of fluid trapped in the section 19.

When the test is completed, the packer 14 is disengaged from the well bore and the string of tools is retrieved to the surface. When sub 20 appears at the rotary table at the surface, the retrieval of the tool string from the well is temporarily halted. The plug 80 is removed from passageway 76 on the sub 20 and a gauge (not shown) is connected to the threaded end 78 of the passageway. The valve 63 is moved by rotation of valve body 65 to open the other end of passageway 76 into communication with flow passage 41 thereby placing the gauge in communication with the closed chamber 19. After measuring the pressure of chamber 19, the valve 63 is closed, the gauge removed, and a flow line is connected to the threaded end 78 of passageway 76. The valve 63 is again opened to permit the pressure in chamber 19 to be bled off into a closed receptacle connected to the opposite end of the flow line.

The valve 63 in again closed and a transfer head or flow line (not shown) is connected to the upper box end of the sub 20. The drop bar 33 is then released by mating the retainer pin 35 which withdraws the end of the pin from the recess 46 in the plug 44. The bar 33 drops through the fluid sample in chamber 19 and shears the plugs 25 to open ports 27 in the reversing sub 18. Blowout preventers at the well head (not shown) are then closed and pump pressure is applied to the well fluid or drilling mud in the well how annulus. This pumps the well fluid into ports 27 and thereby forces the formation fluid sample out of chamber 19 through the now open bore 41 in sub into the flow line attached to the sub and from there into a closed receptacle or pit (not shown) which is disposed a safe distance from the upper end of well. Pumping is continued until the fluid sample has been reversed out. Pumping is then ceased and the flow line disconnected. Upon further retrieval of the tools from the well bore, well fluid and any trace of formation fluid in the pipe will drain out through ports 27 into the annular space in the well.

In testing shallow wells, it may be desirable to use the full length of pipe above the test tools as the sample chamber. In this event, the upper end of the pipe is closed off by means of control valves, etc., at the surface. After the formation test, the test valve is closed. Pressure is bled from the pipe through the surface control valves into a closed receptacle connected to the control valves. A drop bar is then released from the surface to open the break valves in the reversing sub. Pressure is then applied to the well fluid to reverse the formation sample out of the pipe through the surface control valves and into the closed receptacle. The string of pipe and tools are retrieved to the surface and any well fluid or formation fluid in the pipe will drain back into the well bore through the reversing ports 27.

During the above described operations, the formation fluid sample has remained in a closed system to prevent the disclosure of its contents and to prevent the exposure of flammable hydrocarbon fluids on the derrick floor.

In the event the tool string should become stuck in the well, and cannot be jarred loose, the safety joint 16 is backed off to permit retrieval of the tools positioned above the safety joint. The remaining part of the tool string is then fished or drilled out. A further safety feature is embodied in the tool should it be necessary to lower a free point indicator, string shot, or other apparatus into the pipe to loosen the threaded connection of a pipe collar and thereby free the tubing string above the collar.

In order to open the bore of sub 20 to permit a device to be lowered therethrough, the plug 44 is displaced from its posit-ion in bore 41. This may be accomplished by dropping a bar from the surface. Alternatively, the drill stem or tubing above chamber 19 is filled with a fluid. The pressure of the fluid expels the plug 44 and attached dart from the intermediate bore 43 of the sub 20. If the hydrostatic pressure of the fluid itself is insufficient to displace the plug, pressure may be applied to the fluid column to remove the plug. When sufficient pressure is applied to the top of plug 44 by whatever means, the retainer pin 35 is sheared to permit the plug to drop from the bore 41 in sub 20. The bar 33 then drops through the fluid sample to break the plugs and open ports 27 in reversing sub 18. Pressure is then applied to the well fluid in the well bore annular space to pump the fluid into the ports 27 and thereby reverses the formation fluid sample out of chamber 19 while at the same time restoring circulation to the drilling fluid in the well bore. The opening left in the sub 20 by removal of the plug and drop bar is suflicient to pass the free point indicator and string shot.

It will be appreciated from the description above that drill stem testing by this method will minimize any hazard of fire when testing with electrical power equipment operating on the derrick floor such as is necessary at night. Furthermore, by controlling the exposure of formation fluids at the well site, it is possible to maintain the results of the test confidential.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A method for obtaining a fluid sample from earth formations traversed by a well bore containing a well fluid comprising the steps of: positioning packer means on a string of pipe in a well bore where the string of pipe has spaced-apart upper and lower normally closed valves forming a chamber therebetween, the upper valve being adapted for coupling to a closed sample-receiving enclosure, setting the packer means to isolate a section of the well bore from the well fluid, opening the lower valve in the string of pipe to permit formation fluids from the isolated section of the well bore to flow into the string of pipe, closing the lower valve to trap a sample of formation fluid, unsett ing the packer means, raising the string of pipe to a point where the upper valve is accessible at the earths surface, coupling the upper valve to the enclosure, opening the upper valve, opening the string of pipe to the well fluid at a location proximate to the lower valve, and applying pressure to the well fluid to discharge any formation fluids in the string of pipe to the enclosure.

2. A method of recovering a sample of formation fluid from a well bore containing a well fluid comprising the steps of: in a well bore, setting a packer suspended on a string of pipe to isolate earth formations and then opening a test valve to permit the flow of fluid from the isolated earth formations into a section of the pipe having a releasable plug means closing its upper end, closing the test valve to trap the sample in the section of pipe, filling the pipe above the closed section with a fluid, applying pressure to the fluid in the pipe above the closed section to release the plug means from the upper end of the closed section and to open a port at the lower end of the section of pipe, connecting the upper end of the stringv of pipe to a closed receptacle at the surface, and applying pressure to the well fluid to pass the well fluid from the well bore through the port to displace the formation fluid in the section of pipe into the receptacle at the surface.

3. A method of obtaining a fluid sample from earth formations traversed by a well bore containing a well fluid and retrieving the sampling apparatus when it becomes stuck in the well bore, comprising the steps of: in a well bore, setting a packed suspended on a string of pipe and then opening a test tool to permit the flow of fluid from isolated earth formations into a section of the pipe having a plug means closing its upper end; releasing the plug means from the upper end of the closed section to provide an opening through the string of pipe and to open a circulating port at the lower end of the section of pipe; connecting the upper end of the string of pipe to a discharge receptacle at the surface; applying pressure to the well fluid to displace the formation fluid from the string of pipe and into the discharge receptacle; and thereafter locating the stuck point, positioning joint releasing means in the pipe string at a selected joint above the stuck point, releasing the selected joint, and retrieving the string of pipe above the selected joint.

4. A method of drill stern testing in a fluid filled well bore which traverses earth formations, comprising the steps of: lowering a packer, a tester valve and a closed chamber formed by a section of pipe into a well bore on a pipe string; setting the packer to isolate a formation zone from the well fluids; opening the tester valve to communicate the chamber with the isolated zone to permit a sample of formation fluids to enter the chamber; closing the tester valve to trap the sample in the chamber and then releasing the packer; raising the closed chamber toward the surface and, when the upper end of the chamber reaches the surface, connecting the upper end of the chamber to a receptacle; opening the lower end of the chamber; and applying pressure to the well annulus to circulate the sample out of the chamber and into the receptacle.

5. The method of claim 4 including the further step of bleeding off the pressure of the sample before opening the lower end of the chamber.

6. The method of claim 4 including the further step of measuring the pressure in the closed chamber before opening the lower end thereof.

References Cited UNITED STATES PATENTS 2,143,251 1/1939 Savitz 166152 X 2,327,610 8/1943 Savitz 1663 2,645,288 7/1953 Deters et a1 166149 2,661,802 12/1953 Johnston l66165 X 3,038,539 6/1962 Bloom et a1 1663 OTHER REFERENCES Bleakley, W. B.: Modern Drill-Stem Testing," The Oil and Gas Journal, December 1958, vol. 56, No. 51, pp. 58-63.

DAVID H. BROWN. Primary Examiner. 

